This is more of a suggestion to the developer of Portable Firefox, who I hope reads these forums. I don't know if this has been mentioned before but please disable Firefox update by default in future releases. Or at least change the settings so that it won't automatically download and try to install updates. I launched Portable Firefox only to have it try to patch itself to 1.5.0.1 Of course the patch failed so it instead tried to download the entire 6.0 MB installer. I've disabled it myself as of now.
John is fully aware that the partial update (i.e. patch) fails... by all means it shouldn't, but it does. However, the full update will be successful if you let it finish. Portable Firefox still functions normally after being updated, so I can't see any reason to disable updates.
True, a full update--yes, despite its size, this is still an update, not the full interactive installer--will take a while to download over dial-up, but in my experience, Firefox will let you know before it tries to download an update. If you don't want to update it, then you can just tell it not to update. Simple as that.
Just as an aside, the size of the full update is odd in itself: the complete interactive installer for 1.5.0.1 is just under 5 MB, and the full update is anywhere from 6 to 7 MB (not sure of the exact number; it's been a while since I updated).